Polyphenylene oxides obtained by oxidative polymerization of nucleus-substituted phenols are known to be useful resins. In particular, a polymer alloy or polyblend comprising polyphenylene oxide and polystyrene or polyamide possesses excellent thermal, mechanical, and electrical properties and has recently broadened its application as a molding material in various fields.
Many processes for producing polyphenylene oxides by oxidative polymerization of nucleus-substituted phenols are known in the art. The oxidative polymerization is commonly carried out using a catalyst system comprising a combination of a copper, manganese or cobalt compound and a ligand selected from various amines and bases, and many proposals have so far been made on such a catalyst system. Of these, a catalyst system comprising a manganese compound combined with a basic compound such as sodium hydroxide, as described in Japanese Patent Publication No. 30354/70, is noteworthy because of not only good economy but also its high activity. However, this catalyst system has problems such that the molecular weight of the resulting polyphenylene oxide cannot be controlled and the resulting polyphenylene oxide is gelled on heat melting.
In order to solve these problems, the inventors previously proposed a catalyst system comprising monoethanolamine and/or diethanolamine, a manganese compound, and a basic compound as disclosed in Japanese Patent Application (OPI) No. 44625/82 (the term "OPI" as used herein means an "unexamined published application"). It has also been proposed recently to use an N-alkylalkanolamine in place of the monoethanolamine and/or diethanolamine as disclosed in Japannese Patent Application (OPI) No. 8318/85.
According to these techniques, the problem of molecular weight control and gelation on heat melting can be settled. However, the resulting polyphenylene oxide turned out to be still unsatisfactory as a starting resin of a polymer alloy with polystyrene or polyamide. For example, molded articles obtained by injection molding of the aforesaid polymer alloy are of inferior quality, e.g., in planar impact resistance.